Asymmetric anionic polymerizations of N-substituted itaconimides having chiral amino-acid esters

Abstract

Chiral itaconimides bearing the amino-acid methyl ester (MRII), such as phenylglycine-, phenylalanine-and leucine-methyl ester, at the side chain (S)-or (R)-MPGII, (S)-MPAII and (S)-MLII, respectively, were successfully synthesized and then polymerized with organometal-chiral ligand complexes such as n-butyllithium/(À)-sparteine [n-BuLi/(À)-Sp], n-BuLi/(S,S)-(1-ethylpropylidene)bis(4-benzyl-2-oxazoline) [n-BuLi/(S,S)-Bnbox], Et 2 Zn-(À)-Sp and Et 2 Zn-(S,S)-Bnbox in toluene or tetrahydrofuran (THF) to obtain optically active polymers. The effects of polymerization conditions on optical activity and the structure of poly(MRII)s were investigated by gel permeation chromatography (GPC), circular dichroism, specific rotation and 13 C nuclear magnetic resonance measurements. The yields of methanol-insoluble part of the polymer and the M n s, as well as the chiroptical properties of poly(MRII)s, were strongly affected by organometals, ligands, solvents and temperature. The behaviors of poly(MRII)s were different according to N-substituents. In addition, the polymers obtained with n-BuLi as the anionic initiator had higher stereoregularity than those obtained with a radical initiator. Polymer Journal (2011) 43, 516-524; doi:10.1038/pj.2011.17; published online 6 April 2011Keywords: amino-acid ester; anionic polymerization; asymmetric polymerization; itaconimide INTRODUCTION Chiral synthetic polymers are particularly interesting because of their applications as chiral stationary phases for high-performance liquid chromatography, chiral catalysts and chiral reagents. Moreover, for the function of biopolymers such as deoxyribonucleic acid (DNA) and protein, it is important to control secondary structures such as helices. Syntheses of helical polymers, such as poly(alkyl methacrylate)s, 1-3 polyacetylenes, 4-7 polyisocianates 8 and polyisocyanides, 9-11 have been reported by several researchers. Physical and steric interactions between side chains are essential factors in the formation of the helical structures of these polymers. For example, Okamoto et al. [1][2][3] reported that polymerization of triphenylmethyl methacrylate with organolithium/chiral ligand complexes successfully proceeded to yield a polymer with a single-handed helical structure formed by steric repulsion between the bulky side chains. Masuda et al. 12-15 successfully synthesized poly(N-propargylamide)s with a well-controlled helical structure based on hydrogen bonding between the chiral side chains, as well as steric repulsion.We systematically investigated the asymmetric polymerization of N-substituted maleimides (RMIs) and reported properties of the resulting polymer with chiral recognition ability. In recent years, our research focus has been on the asymmetric polymerization of RMIs bearing amino-acid derivative moieties, and we have reported the higher-order structure of polymers induced by hydrogen bonding between the amino-acid side chains. [16][17][18][19][20][21][22][23]

Progress in the Free and Controlled Radical Homo‐ and Co‐Polymerization of Itaconic Acid Derivatives: Toward Functional Polymers with Controlled Molar Mass Distribution and Architecture

“…Examples of functional polymers obtained from itaconic acid derivatives and their applications are also given. While certain itaconic acid derivatives can be polymerized by anionic polymerization or enzyme‐catalyzed/thermally induced polycondensations, [ 15,19–24 ] these reaction types will not be considered in this work. CRP of monomers from renewable resources has been reviewed previously, [ 2,25–27 ] but not with such detailed attention to itaconic acid and its derivatives.…”

JMS Letters

“…[9] The complexes of transition metals and bis-quinolizidine alkaloids have found many applications as useful reagents in organic chemistry. [10][11][12][13][14][15] Some effort has been devoted to the electron ionization and fast atom bombardment mass spectral study for differentiation of ligand, as well as metals in the series of Zn +2 and Cu +2 dichloride (dibromide, diacetate, diformate, dithioacetate) complexes of (-)-sparteine and (-)-aisosparteine. [16,17] Several principles are fragmentally used to predict stabilities and binding preferences: the Irving-Williams series [18] and the hard-soft acid-base concept.…”